1. Technical Field
The present invention relates to a supplementary optical system for a camera which is inserted between a photographic lens and a camera housing and which comprises a relay system for projecting an image of the photographic lens onto film or a video recording medium.
2. Background Information
A supplementary optical system is known from European Patent A-0 690 327. Such systems may be used with still cameras, film cameras, or video cameras. Additional supplementary optical systems of the general type are known from U.S. Pat. Nos. 5,469,236 and 4,867,549. Explicit reference is made to these documents for an explanation of all the features which are not described in detail in this application.
All of the known supplementary optical systems have the feature in common that the normal camera lens, which is directly located on the camera housing, is attached to the supplementary system so that it presents a more or less wide spacing from the camera housing, depending on the design of the supplementary system. Especially when the camera lens is a variable power or zoom lens, this feature renders the operation more difficult for the operator because the controls for focal length adjustment and for operation of other camera elements are spaced at a comparatively wide distance from the camera housing.
It is moreover inexpedient in the known systems in that they cannot be adapted to handle different tasks in a simple manner. For instance, it is not possible to simply use each of the known systems both as a straight system and as a bent system after simple conversion.
The subject invention is now based on the problem to improve a supplementary optical system for a camera in such a way that handling will be facilitated and that the system can be converted for different tasks in a simple manner.
One inventive solution to this problem is defined in Patent claim 1. Improvements of the invention are the subject matters of claims 2 et seq. In accordance with the subject invention the relay system may be structured so that it produces more than one image and so that the lens disposed directly on the camera body is a zoom lens.
It is therefore not only possible to perform focusing and rotation of the image close to the camera, but moreover the image magnification can be selected. In particular, the zoom lens (as a lens with which focusing is varied when the focal length is varied) may be supplanted by a varifocal lens, i.e., a lens in which focusing is not varied when the focal length is varied.
Due to this configuration it is furthermore possible to convert the supplementary optical system of the present invention in a comparatively simple manner. It is possible in particular to select the object-to-lens distance between the image of the photographic lens and the first image to be so wide that further systems such as path-bending units may be accommodated in this zone.
It is particularly preferred that the path-bending unit be disposed between the photographic lens and the relay system because in such a case the optical system, which is arranged in the taking path ahead of the path-bending unit, is of a comparatively small and hence light-weight design.
In another configuration, the path-bending unit comprises two elements of which at least one bends the light path through 90 degrees. With this design in particular an offset of the optical axis can be achieved which enables the operator to manage complicated taking situations, such as those involved in macro photography, by means of the inventive supplementary system of the present invention.
One of these elements may be a front-surface mirror whereas the other element may be a path-bending element with image reversion so that a non-reversed image is obtained with an intermediate image.
The aforementioned design permits not only an offset of the optical axis but also a tilt of the offset optical axis. To this end an element can be rotated together with the photographic lens in such a way that the respective swing angle of the photographic lens amounts to twice the magnitude of the swing angle of the tilting element. The tilting element may be the front-surface mirror in particular.
In a preferred embodiment of the present invention the relay system includes three lenses and the zoom lens, with a prism being disposed for image rotation between the first and the second lenses. The two lenses, which are arranged between the image rotation prism and the zoom lens, are preferably of a similar or equivalent design and preferably are disposed in symmetry relative to the center plane therebetween.
The invention will be described in the following by exemplary embodiments, with reference to the drawings, but without implying any restriction of the general inventive idea. With respect to the disclosure of all inventive aspects which are not explained in more detail in the text, reference is explicitly made to the drawing as well.